Kim Jong Un ordered North Koreans, particularly Christians, on Sunday that instead of celebrating Christmas Day, the country should instead celebrate the birthday of his deceased grandmother.

The dictator's grandmother, Kim Jong Suk, was the wife of Kim Il-sung or the "Eternal President of the Republic," who was the country's first dictator. Jong Suk was born 1919 on Christmas eve.

Called as the "Sacred Mother of the Revolution," Jong Suk was known as a communist who fought against the Japanese. She died in 1949 from "mysterious circumstances," according to the New York Post.

North Koreans visit her tomb on her birthday to pay their respects.

Jong Un has generally displayed hostility toward Christmas and Christians. In 2014, he threatened war with South Korea after it revealed plans to set up a Christmas tree along the border. South Korea later on decided not to put up the tree.

North Korea tops the list of countries where Christians are highly persecuted, according to nonprofit organization Open Doors. Many Christians end up in prison simply for their faith. They are often accused with other crimes and subjected to intense pressure to make them confess to committing the alleged crimes.

Other Christians are held in prison camps where they face torture, hard labor, rape and other forms of harsh punishment for worshiping God.

In November, Amnesty International released a report showing satellite images indicating such prison camps have been upgraded. The security within the camps have also been intensified.

This indicated that the camps are in use despite North Korean authorities' declaration that the prison camps are no longer operational.

"These camps constitute the cornerstone of the country's large infrastructure dedicated to political repression and social control that enables widespread and systematic human rights abuses," Amnesty International said.

"Assessments of the satellite images of two political prison camps - known as kwanliso -- collected in May and August show the addition of new guard posts, upgrading of a reported crematorium, and on-going agricultural activities," the organization said further.

In a 2014 report, Amnesty International revealed various human rights violations in North Korea with atrocities that could not compare with any other country.

People detained in North Korean prison camps, for example, could suffer from various forms of torture, such as starvation and infanticide.

Amnesty International said many of those being held in prison camps did not commit the crimes themselves but were taken in custody by guilt of assocation with persons considered as threats.

Pyongyang used to have the most number of Christians compared to other Korean cities. Today, there are an estimated 50,000 to 70,000 Christians being held in prison camps.